I'm trying to create a database for a hotel company with multiple hotels. I'm stuck on how to reserve a room?

I'm using Xampp phpmyadmin for the first time... So I've got the basics of the database. Customers, hotels, rooms etc. The customer can chose a check-in and check-out date. An admin can class a date as available/not. My question, is how would I get the database to automatically update the dates as unavailable? When I've tried, it makes that date unavailable for every room in every hotel. (Still a newbie at all this, so sorry if this doesn't make any sense!) Attached a rough draught of my ERD for reference.